Feb. II, 1918 Freezing-Point Method and Soil Solution 



389 



Table VII. 



-Comparison of total solids in soil solution as calculated by freezing-point 

 and extraction methods — Continued 



Upon several occasions the total solids were determined in the i-to-5 

 extracts of all soils. These were also calculated in terms of concentra- 

 tion of total soil moisture, as well as of free soil water. From the depres- 

 sions of the freezing point, calculations were made of concentrations 

 expressed as total solids in parts per million of the soil solution with the 

 constant just described (Table VII). The first and most striking observ- 

 ation based on these results is that the relation between the total solids 

 in the extracts of cropped and uncropped soils is also manifested by the 

 depressions of the freezing point. In fact, throughout the experiment 

 this correlation was noted. The fluctuations pf the important nutrient 

 elements in the water extracts already described by Stewart were in 

 general agreement with the changes in the concentration of the soil 

 solution. The low and high points came at about the same periods of 

 the growing season in both cases. 



From these considerations it might seem justifiable to assume that the 

 material present in the actual soil solution forms at least an important 

 fraction of the total solids dissolved in the i-to-5 extract. It is, how- 

 ever, highly improbable that an extract should consist exclusively of the 

 material present in the soil solution. Necessarily an additional quota 

 would be derived from other more or less soluble substances, and the 

 quantity dissolved would depend upon the conditions of extraction. A 

 number of years ago Mitscherlich (6), in an important study on extracts 

 of soils prepared with carbonated water, emphasized this point of view. 

 His procedure consisted in making extracts with varying proportions of 

 carbonated water, ranging from 5 to i up to 30 to i . From the data so 



